Can you please add a test case?

@nicolas-grekas I think it's also a good idea to be able to add custom behaviour in that slugger (for such replacements). I was thinking about callback. What do you think?

be able to add custom behaviour in that slugger

I don't think it's needed: decoration alreadt allows implementing custom behaviors to me.

Thank you@Warxcell.

@nicolas-grekas kinda. You have to make your own instance ofUnicodeString beforeAsciiSlugger,
then pass result from->toString() toAsciiSlugger. Or just use regularstr_* ormb_* functions.

    public function slug(string $string, string $separator = '-', string $locale = null): AbstractUnicodeString    {        $string = new UnicodeString($string);        $string->replace('XX', 'YY');        //  do other stuffs        return $this->asciiSlugger->slug($string->toString(), $separator, $locale);    }

yes
or you replace on the return point (return parent::slug(...)->replace(...);)
or you reimplement completely
etc

@nicolas-grekas no, not exactly. on return point everything is now replaced by $separator - it's too late to do anything else on this string.
The other possibility is method to accept either string, eitherAbstractUnicodeString.

Oh, indeed. Thestring barrier is not an issue to me, it's fine creating the object again inside.